Hello all I have Hp Pavilion X360 LAPTOP, last night I update my windows 10. when windows update is COMPLETED, and restart my PC I pressed the windows key from the laptop keyboard. firstly I THINK this may be the windows error, I restart my Pc again and again, but my problem is not solved, can anyone help me to out this? Waiting for Your Help and Suggestions!
Thank You.Your laptop was supplied with a 120 gb Hard drive as the laptop is still quite new and the drive is electronic it is most likely the drive is full. If you try powering up the laptop holding the F12 key it should start to the safe mode menu. Then you can select command prompt. Then run DIR enter to check the used space and free space on the drive. If there is kb free windows won't be able to complete starting up.

You will need a bigger SSD drive, here is a video of how to change the drive https://www.youtube.com/watch?v=0iR4wUmTjQI

if it isn't a HDD short of space then you could roll back the latest update. Copied this from https://sourcedaddy.com/windows-10/roll-back-updates.html

To use the Go Back To Previous Windows version in Advanced Startup, use these steps.

Boot to advanced startup options.( You can do this by powering down and up the laptop 4 times without loading windows then it will go into the recovery mode)
In the Choose An Option dialog box, click Troubleshoot.
On the Troubleshoot page, click Advanced Options.
On the Advanced Options page, if you don't SEE Go Back To The Previous Build, click See More Recovery Options if displayed.
Click Go Back To The Previous Build.
On the Go Back To The Previous Build page, select an administrator account and enter the password for this administrator account.
Click Continue.
On the Go Back To The Previous Build page, click Go Back To Previous.
Your computer restarts, and the EARLIER build of Windows now starts restoring.Thanks for the reply and sorry for the last response, I found the solution here: https://answers.microsoft.com/en-us/windows/forum/windows_10-start-winpc/windows-10-start-button-not-working/765f193c-4c67-4b85-81e0-645dfd29836c official site of the Microsoft and https://techsherlock.com/windows-10-start-menu-not-working/ found on the Internet. i Follw the step provided in the Site. My Problem is solved now.
Thank You